Material mixture, sputter target and method for producing a sputter target

ABSTRACT

A material mixture is produced having a cobalt-based alloy as the predominant component and an additional component of at least TiO x . The material mixture may be formed into a sputter target by hot pressing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of International Application No. PCT/EP2006/009766, filed Oct. 10, 2006, which was published in the German language on Apr. 19, 2007, under International Publication No. WO 2007/042255 A1 and the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a material mixture comprising a cobalt-based alloy as the predominant component, a sputter target, and a method of producing the target.

Material mixtures comprising a cobalt-based alloy as the predominant component are known, for example from U.S. Pat. No. 6,759,005 or from German published patent application DE 195 08 535 A1. These material mixtures are used, inter alia, to create thin layers as magnetic function layers, especially in magnetic data storage technology; or the material mixtures form these layers. Due to the requirements for a high capacity of these layers, the requirements on the layer materials are increasing and thus on the sputter targets, which are used for production of the layers, since these layers are preferably produced by sputtering.

BRIEF SUMMARY OF THE INVENTION

The invention is based on the objective of improving the known material mixtures with regard to their magnetic properties.

The objective is achieved by a material mixture having a cobalt-based alloy as the predominant component, i.e., having a percentage of more than 50 weight %, which additionally comprises at least TiO_(x) as the lesser component. The material mixture has significantly improved magnetic properties and is thus, as a thin layer, more suitable for magnetic data storage. Such materials are preferably deposited as thin layers by a sputter technique. Particularly good homogeneity in depositing sputter material on a substrate from a sputter target comprising the material will be achieved by the oxygen-reduced (sub-stoichiometric, i.e., x<2), electrically conductive titanium oxide being present as a powder with a particle size ranging from 0.1 to 50 μm. In the TiO_(x) compound, x is preferably between 1.5 and 1.998.

The material mixture or, respectively, a sputter target produced therefrom is preferably formed from the oxide powder and a metallic powder of the cobalt-based alloy. The sputter target preferably has a density of at least 95% of the theoretical density of the material. The sputter target is produced such that a powder of the cobalt-based alloy is mixed with the TiO_(x) powder, and the powder mixture is hot pressed. It is here advantageous that the powder mixture is pressed hot axially or hot isostatically. The material mixtures according to the invention will result in storage media of very high capacity. They have a TiO_(x) percentage of preferably 15 mol % maximum.

A metallurgical melt production of these material mixtures or the corresponding sputter targets is difficult or impossible, since the ceramic TiO_(x) does not alloy with the cobalt-based alloy. As a rule, mechanical stirring of TiO_(x) particles into a cobalt-based alloy melt does not result in a homogeneous material. Powder metallurgical production methods are also problematic, since there is, on the one hand, a mixing problem between metallic particles and ceramic particles and, on the other hand, a technical sputter problem because failures in the sputter process will result if electrically insulating ceramic particles are present in sputter targets. Surprisingly, these problems were also solved by the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is explained by the following exemplary embodiments.

Example 1

In a tumble mixer, 880 g of an inert gas atomized powder of a cobalt chromium alloy having a chromium part of 12 weight % is mixed for 24 hours with 120 g of a powder of pre-treated TiO_(x). The mixture can also be prepared by other standard mixing methods, for example with a ball mill or a drum mixer. The TiO_(x) powder is pretreated by vacuum annealing in a reducing atmosphere at a temperature of approx. 1400° C. The oxygen content in the TiO_(x) powder is reduced by the oxygen-reducing annealing by approx. 2 weight % (versus the stoichiometric oxygen content). Thereafter, the reduced TiO_(x) powder is screened with a screen of 50 μm mesh size. In a tumble mixer the TiO_(x) powder having a particle size of less than 50 μm is homogeneously mixed, for 24 hours, with the powder of the cobalt chromium alloy.

Thereafter, the resulting mixture of the cobalt chromium alloy and 9 mol % TiO_(x) is filled into a hot pressing form and compressed in a vacuum press at 1100° C. with a compacting pressure of 30 MPa. The accordingly hot-pressed sputter target from the described material mixture (CoCr12 TiO_(x)) has a relative density of 98.0% of the theoretical density. A metallographic section preparation shows a very homogeneous distribution of the electrically conductive TiO_(x) particles in the cobalt alloy matrix.

Example 2

A material mixture and sputter target having the composition Co/Pt18 at %/Cr10 at %/TiO_(x)8 mol % were produced analogously to the method of Example 1.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

1. A material mixture comprising a cobalt-based alloy as a predominant component and a component of lesser amount comprising at least TiO_(x), wherein x is the atomic ratio of O to Ti.
 2. The material mixture according to claim 1, wherein in the component TiO_(x), x<2.
 3. The material mixture according to claim 2, wherein in the component TiO_(x), 1.5<x<1.998.
 4. The material mixture according to claim 1, wherein the component TiO_(x) is in particle form having a particle size in a range of 0.1 to 50 μm.
 5. The material mixture according to claim 1, wherein the mixture is a mixture of a metallic powder of the cobalt-based alloy and an oxide powder of the TiO_(x).
 6. The material mixture according to claim 1, wherein the cobalt-based alloy is an alloy of cobalt with at least one metal selected from chromium, platinum, tantalum, and boron.
 7. A sputter target produced from a material mixture according to claim
 1. 8. The sputter target according to claim 7, wherein the target has a density of at least 95% of a theoretical density of the material mixture.
 9. A method for producing a sputter target according to claim 7, the method comprising mixing a powder of the cobalt-based alloy with a powder of the TiO_(x), and hot-pressing the powder mixture.
 10. The method according to claim 9, wherein the powder mixture is pressed hot axially or hot isostatically. 